1. Field of the Invention
The present invention relates to a transmission for vehicles, and more particularly, to a transmission for vehicles with an improved mounting structure for a parking gear used to fix a vehicle to be parked.
2. Description of the Related Art
Among transmissions for vehicles (automobiles), there is one called a double-clutch (or twin-clutch) transmission. The double-clutch transmission is composed of two clutch devices and a gear mechanism in which drive gears and driven gears continuously mesh with one another. Thus, the double-clutch transmission has an effect that it can perform a continuous speed change operation with a short time lag and power transmission with little loss.
In general, moreover, an automatic transmission is provided with a parking gear. When the transmission is set to the parking position, the parking gear is engaged and fixed by a pawl portion. Thereupon, output shafts of the transmission are fixed so that the parked vehicle is prevented from moving unexpectedly.
If the vehicle is parked in an inclined place, on the other hand, its weight acts on the parking gear and the pawl portion via drive gears. In consequence, an excessive load is applied to the parking gear.
A double-clutch transmission that copes with this situation is described in Jpn. Pat. Appln. KOKAI Publication No. 2006-52832. This transmission is provided with four driven gears for first, second, third, and fourth gear positions on a first output shaft and three driven gears for fifth, sixth, and reverse gear positions on a second output shaft. A parking gear is provided between the third and fourth driven gears.
In the transmission described above, however, the parking gear is situated between the other gears, so that the output shafts are inevitably long. Therefore, the transmission also has a large axial dimension, so that an engine that is provided with the transmission is inevitably large as a whole. Further, the transmission of this type requires more component parts and entails machining operations for the parking gear to be mounted on the output shaft and much trouble of assembling the parts.
There is also a front-engine, front-wheel-drive (FF) vehicle that incorporates an engine, transmission, drive mechanism, steering mechanism, etc., in its front part. In transversely mounting the engine in the FF vehicle arranged in this manner, the axial dimension of the transmission, in particular, is expected to be reduced so that the engine can be easily assembled without interfering with the steering mechanism, side members, etc.